Temporal and vertical persistence of the non-native rotifer Kellicottia bostoniensis (Rousselet, 1908) during water stratification and mixing of a deep tropical reservoir

The non-native rotifer Kellicottia bostoniensis (Rousselet, 1908) has been recorded for ten years in an oligotrophic monomictic deep tropical reservoir in southeastern Brazil, where this study was conducted. This study evaluated how water column conditions in this reservoir influence the occurrence and density of K. bostoniensis throughout the year. The occurrence and density of K. bostoniensis, phytoplankton composition, and physical and chemical variables were assessed from the surface to 40 m depth at the dam area for two consecutive years. The effects of seasonal stratification and dry-season mixing were analyzed using nonparametric tests and linear mixed-effects models (LMM). K. bostoniensis occurred throughout the water column, with significantly higher densities during the dry seasons. Nano-phytoplankton was positively associated with K. bostoniensis density, whereas cyanobacteria showed a negative relationship, indicating that food composition and size structure, rather than total algal biomass, is a key driver of population dynamics. K. bostoniensis exhibited higher densities at intermediate depths (5–25 m), and its vertical distribution was positively associated with the dissolved oxygen levels. Overall, our findings advance the understanding of the ecological drivers underlying the distribution of K. bostoniensis , highlighting how this non-native species responds to interacting vertical gradients and seasonal dynamics in tropical reservoir systems.